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Playing Around With Stems

Top Doggery

My pear trees look as if a giant spider went on a drunken frolic among the branches. Rather than fine silk spun in an orderly web, strings run vertically from branch to branch and branch to ground. Yet there is method in this madness. Mine.
 
As I spell out in my new book, The Ever Curious Gardener: Using a Little Natural Science for a Much Better Garden, plants produce a natural hormone, called auxin, at the tips of their stems or at high points along a downward curving stems. This hormone suppresses growth of side branches along the stem, allowing growth from a bud at the stem tip or high point be the “top dog,” that is, the most vigorous shoot.

Within any plant a push and pull goes on between fruiting an stem growth. Both require energy, which the plant has to apportion between the two. The more vigorously growing a stem, the less fruitful it is.

All this talk of hormones and inherent stem vigor is more than academic; it can translate into delicious fruits.

Pear trees tend to grow very vigorously, especially in their youth, with many vertically oriented branches. A certain amount of stem growth is, of course, desirable; leaves are needed for harvesting sunlight for energy and stems are needed on which to hang fruit.
Tied branches in British orchard

Tied branches in British orchard


But pear trees, especially in the youth, tend to put too much of their energies, too much for me, at least, into stem growth. The result is that they can take long time to settle down and begin bearing fruit.

Hence, the strings. I can change my pear trees’ habits by merely tying down branches, reducing the effect of that auxin so that growth is more uniform along a length of the stem. And, as important, slowing growth nudges the energy balance in the direction of fruiting.

Branch bending

The one branch on each young tree that I do not tie down is the main vertical stem, which is the still developing trunk off which grow the main side branches. I want this stem to keep growing upward. Also, I have to be careful not to create a downward arch when tying down any stem. You know why: a very vigorous shoot pops up from the high point in that arch.

More Fruit or More Growth?

Branch bending is not only for coaxing a tree into fruiting. On young branches, it creates a wide angle between a branch and the developing trunk. Wide angles here have been shown to result in good anchorage, sturdy side branches that can carry a weight of fruit.

Suppressing the vigor of side branches also ensures that they won’t compete with the developing trunk, which needs to be top dog.

And using string to play around with plant hormones isn’t needed on every fruit tree. At the other extreme from pear in its growth and fruiting habits is peach. Peach is naturally very fecund, and becomes naturally so at a very young age.

One reason for peach’s fecundity is that it bears all its flowers and fruits along stems that grew the previous season. Every year new stems grow that bear flowers and fruits.             

Beauty, Fruit, and Fun

All this concern with auxin, vigor, and fruiting comes most prominently into play with espalier, which is the training of a tree to an orderly, often two dimensional form. The tracery of the branches themselves adds to the decorative value of the plant.Pear espalier

Fruiting espaliers, besides being decorative, produce very high quality fruit. Pruning and branch bending maintain a  careful balance between yield and stem growth, and the form of the plant allows leaves and fruits to bathe in sunlight and air.

Asian pear espalier flowering

IT’S ALL ORGANIC, BUT NOT NECESSARILY ALL GOOD

Hay, Grass Clippings, Manure, Leaves — Watch Out!

Organic materials — that is, things that are or were once living — are the core of “organic” agriculture, and right from the get go, many years ago, I set out pitchfork in hand to gather these materials. Into large garbage pails toted around in my van I loaded manure from nearby stables. Neighbors let me haul away their bags of autumn leaves.

I even convinced city workers to dump a truckload of harvested lake weeds onto the side lawn of my small rented house. (That was in Madison, Wisconsin, where fertilizer runoff from lawns was spurring growth of lake weeds which, besides making swimming hazardous, were, upon their death, causing oxygen depletion of the lakes.)

Me mulching, even as a beginning gardener

Me mulching, even as a beginning gardener

Mowings of roadside hay, which I stuffed into the back of the van, were another source of organic matter, used for mulch and for compost. That was before the days of lead-free gasoline, so lead contamination was some concern. Then again, high levels of organic matter in the soil mitigate lead hazards in soils.

More dramatically of concern were bags of grass clippings I once dragged across the yard from my neighbor’s freshly mowed lawn. Hours after I had spread the clippings around my potato’s lush, green vines, their stems twisted and contorted as if screaming in pain — the effect of weedkiller used on the lawn. Perhaps my neighbor was striving for a uniform greensward; perhaps he had inadvertently used a lawn fertilizer laced with weed killer. “Weed and feed” sounds so cheerful and labor-saving. Lawn weedkillers are toxic to broadleaf plants, which means anything but a grass.

The particular weedkiller was probably 2,4-D, also know as Agent Orange (less cheerful-sounding), which is a synthetic category of plant hormone called auxins. At the right concentration and at the right time, whether natural or synthetic, auxins do good things, such as bending plants towards light, initiating root growth in cuttings and in growing plants, and promoting upward growth Otherwise, they can wreak havoc.

I phoned the university extension specialist and was advised to remove the mulch and to adsorb any escaped 2,4-D by mixing activated charcoal into the soil. I did so and subsequent growth was normal.

Home-Grown vs. Imported Hay

I now have the luxury of scything much of the organic material I need from my own one acre field. Early season mowings are succulent and nitrogen-rich, just like grass clippings. Later mowings are hay, dry and carbon-rich. During the growing season, depending on what and when I mow, I can harvest either end of the spectrum, or anything in between.

Wood chips are another good source of organic material, one free of chemicals

Wood chips are another good source of organic material, one free of chemicals

I no longer rely on roadside mowings as organic material for my plantings. They are nowadays too finely chopped for easy and fast scooping up with a pitchfork. Even if that were not the case, I would have second thoughts about bringing such hay on-site. Again, weedkillers are the threat, more insidious these days because of use of more persistent ones. So-called pyridine carboxylic acid weedkillers might hang around in the soil or on sprayed vegetation for anywhere from less than 30 days to several years, even in the manure from animals that have eaten sprayed vegetation!

Caution, Testing, & Time to Avoid Problems

I do still occasionally supplement home-harvested organic materials with imported ones. One source is horse manure from a local stable.

A few weeks ago I was pitching forkful after forkful of manure into the bed of my pickup truck when I glanced over at the far side of the pile and noticed some discarded hay, much of it still pressed together in partial bales. “How convenient,” I thought, for mulching, compost, or bedding for my chickens and ducks.

On my drive home I started thinking about that hay riding behind me. Could it be laced with weedkiller?

For the most straightforward answer, I could just ask the stable owner. A stable hand told me that the hay had been shipped from a few hours away. Rather than cross examine my manure donor, I looked closely at the hay to see if any clover, alfalfa, or other broadleaf plants were mixed in. No. Of course, lack of broadleaf plants does not prove that weedkiller was used.

Well-formed leaves indicate that the hay is free of chemical residues

Well-formed leaves indicate that the hay is free of chemical residues

My final recourse was to do a bioassay of the hay, essentially, to plant seeds in it and observe their growth. Two 4-inch flowerpots, one with chopped up, homegrown hay and the other with the chopped up, imported hay, served as growth media, into which went 3 bean seeds each. Long story short: Growth seemed normal in the imported hay although germination was slower, probably because its texture lent itself to more readily drying out.

To put my mind thoroughly at ease about the hay, I’m going to let the pile sit for a few months, where rain, sun, and, eventually warmth, can do their job in splitting apart the insidious weedkiller molecules. The hay is not for my compost, in the dark innards of which weedkillers, if present, would be particularly persistent.

Autumn Leaves, Good Stuff

Just like the old days, I do still import organic materials in the form of bagged autumn leaves — except a lot more these days. They are both weed- and weedkiller-free.

New Video from Last Summer: Grape Training & Pruning

If you’d like to join me on a brief journey back into summer, see www.leereich.com/videos for a new video, I made last summer, about how to prune that quintessential summer vegetable, tomatoes, just like the Godfather.

Fruit, Grain, & Vegetable

Homegrown Persimmons, Popcorn, and Brussels Sprouts, All in Abundance

It’s raining persimmons! And every morning I go out to gather drops from beneath the trees. And every afternoon. And, depending on the wind and the temperature, sometimes early evenings also.Szukis persimmons in hand

The fruits are delicate, their soft jelly-flesh ready to burst through their thin, translucent skins. Most fruits survive the trip from branch to ground unscathed because of the close shorn, soft, thick lawn landing pad that awaits them. I pop any that burst right into my mouth or else toss them beyond the temporary, fenced-in area as a treat to my the ducks or to Sammy, my dog who has developed a taste for the fruit. (The ducks, Indian Runners, hardly fly but Sammy, if he put two and two together, could easily hop the low fence and beat me to the fruits.) Repeatedly gathering fruit through the day is needed to keep ahead of scavenging insects.

Diopsyros Szukis on lfls tree

Szukis persimmons, ready to eat even from leafless branches

American persimmons grow wild throughout much of the eastern part of our country, about as far north as the Hudson Valley. Wild trees bear either female or male flowers. Males, which never bear fruit, can each sire a few females, which are the ones that do bear fruit. Puckery flavor is the main problem with wild persimmons. They can make your mouth feel like a vacuum cleaner is at work within. All American persimmons elicit that unpleasant feeling until fully soft, colored, and ripe; some elicit the feeling, in some measure, even when ripe.

Planting a named variety can spell the difference between a fruit to spit out and a fruit to swoon over. Said variety needs to be one that, besides tasting good, ripens within the growing season, and isn’t harvested until dead ripe. (Many otherwise good varieties do not have time to ripen this far north.) Szukis and Mohler do particularly well here near the northern limit for persimmon growing, Mohler beginning its ripening at the end of August, and Szukis the end of September. Both varieties ripen fruits over a long period, for a month or more.

One more asset for Mohler, Szukis, and some other varieties is that they make males superfluous. They can set fruit parthenocarpically (without pollination) and/or by pollination from their own occasional male blossoms. Most Mohler and Szukis fruits are seedless, a sign of parthenocarpy, but occasional fruits have a seed or two, indicating that some pollination took place.

Once leaves drop from these trees, fruiting is not finished. Ripe, orange fruits will cling for weeks to bare branches like Christmas ornaments, although, with time, fruits shrivel and brown, losing their visual — but not gustatory — appeal. Not bad for a tree that needs nothing in the way of pruning or pest control, eh?

Popcorn’s Not Just for the Movies

With the fruit course out of the way, let’s move on to the grain course. I’ve tried growing wheat and rice on a (very small) garden scale, and yields were paltry and sometimes difficult to get at because of topheavy plants flopping to the ground. Flopping was probably due to too much fertility and moisture. Processing either grain was a project in itself, entailing removal of the grain from the stalks and then from their husks.Popcorn ready for harvest

The easiest grain to grow and process on a backyard scale is popcorn, which revels in my soil’s good fertility and moisture. I grow popcorn the same way as sweet corn, in “hills” (which, horticulturally speaking, are stations or clusters rather than raised mounds) with 3 to 4 plants per hill and two rows of hills in each 3 foot wide bed, with two feet from hill to hill within each row.

The only downside to growing popcorn on a small scale is the need to keep it away from sweet corn, if you grow that also. Planting sweet corn and popcorn too close to each other lets them cross-pollinate, resulting in sweet corn that is less sweet and popcorn kernels than wanly split to exhale steam rather than blow apart till they’re inside out.

Even with popcorn grown in sufficient isolation, correct moisture level (20 percent) is what makes for good popping. I wait to harvest until the ears and husks are dry on the stalks. After harvest, I peel back the husk, leaving a few layers, pull off the browned silk, then tie 3 or 4 ears together by their pulled back husks and hang the bunch from the kitchen rafters to dry.

The ears hang from the rafters all year ready for popping. When I feel like eating some popcorn, I just twist the kernels off a cob; microwavers can put the cob, intact, into their microwave ovens. I find that poppability varies through the year, probably depending on the temperature and the humidity.

If I sought maximum poppability, I could measure the moisture level by accurately weighing out a portion of kernels and drying them in a 150°F. oven overnight, then re-weighing them. But how big the kernels can puff up isn’t nearly as important to me as the fact that popcorn is an easy-to-grow, nutritious, whole grain that’s tasty and fun to eat.

The Sprouts Responded to Being Pinched

Finally, moving on to the vegetable course. A few weeks ago I wrote about sizing up the sprouts of Brussels sprouts by pinching the tips of the plants. That stops the production of the hormone auxin, which had been suppressing sprout growth further down along the stem.

Pinched Brussels sprouts plants have larger sprouts

Pinched Brussels sprouts plants have larger sprouts

The suppression is only temporary. As uppermost buds start to grow, they, in turn, start pumping down auxin. Those 3 or 4 upper buds now threaten to expand to become stems. At this point they can do what they will because lower buds — the sprouts — have all puffed up to good size.

Hormones Get Pumping

More Brussels Sprouts, Cabbages, & Pears with Hormones

It’s time to get the hormones pumping. No, not by me embarking on some testosterone-fueled, garden-related feat of strength or endurance. Not even my own hormones, but the ones in my plants, more specifically my brussels sprouts plants. And actually, quashing the action of one hormone so that other hormones can come to the fore.

Let me explain: Brussels sprouts are not only a member of the cabbage family but are the same genus and species as cabbage, as are broccoli, cauliflower, kohlrabi, and kale. Differences in these plants lie in the way growth of the stems and leaves are expressed. Cabbage has a single stem that’s been telescoped down to very short internodes, resulting in a tight head of overlapping leaves. With kale, internodes along the stem are further apart, allowing each leaf to unfold fully on its own. They also look different from those of cabbage.

In every plant, a shoot bud develops in the upper part of the crotch where a leaf joins a stem. Most brussels sprouts buds each start to develop enough to form a small, cabbage like head. But I — and probably you also — want large brussels sprouts sprouts (and more of them, so I also want tall brussels sprouts plants on which to attach the sprouts).

Pinching makes Brussels Sprouts sprouts bigger

Pinching makes Brussels Sprouts sprouts bigger

The sprouts are retarded somewhat in their development by a hormone called auxin. Auxin is one of many plant hormones coursing about within leaves, fruits, shoots, and roots, their effect dependent on such variables as plant part, plant age, and what other hormones they are reacting with. One place of auxin synthesis is in the tips of stems, and their effect is to suppress growth of buds down along the stem, with more suppression the closer a bud is to the tip of the stem. I just looked at my brussels sprouts plants; yes, the largest sprouts are those nearest ground level. It’s still too early to harvest and too many of the upper sprouts, at present, are too small to be worth picking.

Suppressing auxin production in the tip of the stem releases their hold on the buds — that is, the sprouts — along the stem, so they can grow larger. Suppressing auxin production is simple, requiring only two fingers: Just snap off the tip of the stem. No tip, no auxin production, for a while, at least. The time to do this “operation” is the beginning of September. Done too soon, and a developing sprout might grow so bold as to grow out into, at worst, shoots or, less worse, loose heads. Plus, earlier in the season, I want to keep the stem elongating to provide real estate along which to hang more sprouts.

A Three-Headed Cabbage!

As I wrote, every plant develops buds in its leaf axils, and in every plant growth of those buds is mediated, in part, by auxin. Harvest the main head of broccoli and side shoots start to grow for eventual harvest.

Even tight heads of cabbage have those buds and they also respond to auxin’s influence. I used to plant cabbage in the spring for harvest in summer. Rather than pulling out the spent cabbage plants, as is usually done, I would leave the cut stump with a few bottom leaves for nourishment. Harvesting the cabbage dramatically removes the tip of the stem, which was buried within the head.

Cabbage plants left after harvest develop multiple heads

Cabbage left after harvest = multiple heads

Within a couple of weeks, new sprouts would develop in the crotches where leaves were or had been. In the ideal world, I’d get one to three new cabbage heads from each plant, ready for autumn harvest. A certain amount of art was needed to get it right. Depending on growing conditions and the number of new heads I allowed to develop, they might end up too small or too loose-leaved.

I’ve abandoned that chancy cabbage habit and now do a second sowing of cabbage in early June for a reliable autumn harvest of firm heads.

Pears — More, Please

I fiddled around with hormones earlier this season also, with longer term goals in mind. Auxin keeps the tip of a stem or the upper portions of a plant growing most vigorously. Vigorous growth, though, is at odds with making fruit. After all, both require a lot of a plant’s energy, so the plant has to partition the energy efficiently between growing and fruiting.

Fruiting pear branchPear trees are famous for growing vigorous shoots skyward. Yes, shoot growth is needed on which to hang fruit and for adequate leaves for photosynthesis. But enough is enough. Rather than pinch out shoot tips, which would likely just pass on the vigor to nearby lower buds, I bent ranches down and held them there with string. Changing stem orientation from vertical to at or near horizontal quells auxin production, slows growth, and promotes the formation of fruit buds along the stem. (Fruit buds form the year before flowers open.)

Fruits now dangle from some of the stems that I pulled down a year ago last spring. The response can take more than a year as energy reserves are redistributed within the stem. Response also depends on a tree’s inherent vigor, growing conditions for the season, the pear variety, the degree of stem bending, and other knowns and unknowns. It’s takes a mix of science, art, and experience, and that’s what makes gardening so interesting for me.